I found that the easiest thing to work on that gives you a feeling of constant progress while also forcing you to learn a vast array of skills is game developme

I found that the easiest thing to work on that gives you a feeling of constant progress while also forcing you to learn a vast array of skills is game development. Making games requires you to learn about data structures, algorithms, optimization, and providing a good user experience all while making something that's enjoyable for yourself. Even if you don't ever plan on making games in the future, the process makes you seek out new knowledge and better methods of implementing everything, plus it also gives you the chance to work with a bunch of different areas of design (UI, controls, AI, possibly networking, graphics/shaders, and loads else), so you might find one subject you like more than the others and discover your specialty. As for motivation, that's unfortunately something that you have to find for yourself. Once you start working on a satisfying project, you won't want to stop. The hard part is finding something that's satisfying.